1. Field of the Invention
The present invention relates to a photographing optical lens assembly, and more particularly to a photographing optical lens assembly comprised of three lens elements for a wide-angle view and applied to electronic products.
2. Description of the Related Art
As mini electronic products such as digital still cameras and mobile phone cameras generally come with an optical lens assembly for photographing an object. The optical lens assembly tends to be developed with a compact design and a low cost while achieving the effects of good aberration, high resolution and high quality of images.
In general, a conventional optical lens assembly of a mini electronic product comes with different designs including the two-lens, three-lens, four-lens, and five-lens design. Although the optical lens assembly with the four-lens or five-lens design has advantages on aberration correction and modulation transfer function (MTF), yet the cost is higher. On the other hand, the two-lens optical assembly hardly can meet the high resolution requirement, and thus the three-lens optical assembly is generally taken into consideration for the design, such as those disclosed in U.S. Pat. Nos. 7,468,847, 7,423,817, and 7,679,841, Japanese Pat. No. JP2008139853 and WIPO Pat. No. WO2010026689.
In recent years, web cams or wide-angle optical lens assembly becomes increasingly popular, and the demand for automobile or monitoring cameras becomes increasingly higher. Therefore, various types of wide-angle optical lenses with a fixed focal length are introduced. A conventional three-lens wide-angle mini optical lens assembly, a combination of different positive or negative refractive powers is adopted, as disclosed in U.S. patent Nos. US2009/080089, US2010/157443, US2010/231686 and U.S. Pat. No. 7,301,808, wherein a combination of positive refractive power, negative refractive power and positive refractive power are used for the design, but the total length of the optical lens assembly cannot be reduced effectively for the purpose of achieving a high imaging quality. U.S. patent No. US2006171042 adopts a combination of negative refractive power, positive refractive power and positive refractive power for the design, but the viewing angle is relatively too large, and it is difficult to shorten the total length of the optical lens assembly. To meet the high-quality requirement of the optical lens assembly, a better design with a good compensation of aberration is required, and the total length of the optical lens assembly can be limited for the use in the mini electronic devices. The invention provides a practical and feasible design that uses the refractive power of the three lens elements and the combination of convex and concave surfaces to increase the viewing angle and shorten the total length in addition to achieving high image quality for the application on compact electronic devices.